(1) Field of the Invention
The present invention relates to a pattern transfer mold and to a transfer system for employing the pattern transfer mold, and relates particularly to a fine structure transfer mold, with which the nanoimprinting transfer of a fine pattern can be performed very accurately, at a low cost, and a fine structure transfer system for employing this mold.
(2) Description of Related Art
Conventionally, photolithography technology is employed for processing fine patterns required for semiconductor integrated circuits. However, in consonance with developments in the structural refinement and the integration of circuits, required element sizes have been reduced until they are the equivalent of the wavelengths of light sources used for photolithography exposure, and fabricating such fine patterns using photolithography is difficult. Therefore, instead of a system that employs photolithography, one that uses electron beam lithography, a type of charged particle beam lithography, has begun to be employed.
For the formation of a pattern using an electron beam, employed is a direct writing method, for which a light source such as an i-line (a type of ultraviolet ray) or an excimer laser is used, that differs greatly from the conventional full projection method. However, a fundamental disadvantage of the direct writing method is that whereas the time required to complete one pattern is normally not excessive, to complete a number of patterns an extended period is required, since the time needed would be a multiple of that for a single pattern. Thus, as the level of integration for semiconductor integrated circuits has been increased, throughput has been reduced, which has led to the development of a full pattern irradiation method, whereby, to increase the speed of the electron beam lithography system, variously shaped masks are employed together and are collectively irradiated by an electron beam to form a mask pattern having a complicated shape. However, with this system, when the situation is such that the refinement of patterns is continuous, associated system costs rise, i.e., the size of the electron beam lithography system is increased and accurate control means, for positioning the masks, must be provided.
On the other hand, a technique for the low cost forming of a fine pattern is disclosed, for example, in U.S. Pat. Nos. A1-5,259,926 and A1-5,772,905 and in “S. Y. Chou et. al., Appl. Phys. Lett., vol. 67, p. 3114 (1995)”. According to this technique, a stamper is used to emboss a resist layer, deposited on the surface of a substrate, with a desired, but inverted, fine, convex-and-concave pattern to be formed on the substrate. As a result, the desired fine pattern can be transferred to the substrate, which, especially according to the nanoimprint technique described in U.S. Pat. No. A1-5,772,905 or “S. Y. Chou et. al., Appl. Phys. Lett., vol. 67, p. 3114 (1995)”, is a silicon wafer, to be employed as a mold, to which and on which a fine, 25 nanometer or smaller structure can be transferred and collectively formed.
Further, the following imprinting method is described in U.S. Pat. No. A1-5,772,905 and “S. Y. Chou et. al., Appl. Phys. Lett., vol. 67, p. 3114 (1995)”. According to this method, a mold is placed on a substrate on which a resin coat has been deposited, and the substrate is mounted on the stage of a parallel plate pressing system, which pressurizes and heats the substrate at the glass transition temperature for the resin, or higher. Then, the substrate is cooled at the glass transition temperature, or lower, and is released from the mold to complete the pattern transfer process.
Furthermore, an imprinting method that employs a roller to apply pressure is disclosed in “Hua Tan et al., J. Vac. Sci. Technol., B16(6), p. 3926 (1998)”. According to this document, a mold is mounted around a roller and is used to imprint a fine pattern having a width of 700 nm and a height of 60 nm. Also in the description given in “Hua Tan et al., J. Vac. Sci. Technol., B16(6), p. 3926 (1998)”, a roller is used to apply pressure to a flat plate mold to form a fine pattern line 70 nm wide and 40 nm long.
However, the following problem has been identified for the above described nanoimprint technique for accurately forming a fine pattern. For example, when the method described in U.S. Pat. No. A1-5,772,905 and “S. Y. Chou et. al., Appl. Phys. Lett., vol. 67, p. 3114 (1995)” is employed to imprint a pattern on a substrate, the heating, pressure application, cooling and release processes must be sequentially performed. Therefore, an extended period of time is required for one pattern imprinting cycle, and it is difficult for this method to be employed for the mass production of a fine structure. As for the method described in “Hua Tan et al., J. Vac. Sci. Technol., B16(6), p. 3926 (1998)”, the substrate is released (separated) from the mold immediately after the substrate has been heated and the pattern imprinted on the substrate. Thus, the aspect ratio (the pattern height/the pattern width) for a pattern to be imprinted tends to be low, e.g., 0.086 (60 nm/700 nm) or 0.57 (40 nm/70 nm), and it is difficult to use this method for a device, such as an optical device or a bio-device, that requires a fine structure having a high aspect ratio (e.g., an aspect ratio of 1 or greater).
As a measure for resolving these problems, a nanoimprint technique is proposed that employs a long belt mold on which a fine pattern has been formed (e.g., JP-A-2006-326948). According to this method, since the heating, pressure application, cooling and releasing processes for the pattern transfer can be sequentially performed, a pattern having a high aspect ratio can be rapidly transferred.
Generally, a semiconductor processing technique is required to form a fine pattern for which the size is several or fewer μm. However, at present, since the maximum diameter of a sample wafer to be processed is substantially 300 mm, it is difficult for a fine pattern to be directly formed on a long, large dimension belt-shaped mold. Therefore, there is a common request for a method whereby a long, highly reproducible belt-shaped mold, used for transferring a fine pattern, can be stably manufactured, i.e., for the provision of a long, belt-shaped mold, with which a fine structure having a high aspect ratio can be rapidly and stably formed (while the abnormal deformation or the snapping of a material, to which a pattern is to be transferred, is prevented).